Digital lighting technologies based on light-emitting diodes (LEDs) offer a massive improvement in comparison to traditional fluorescent and incandescent lamps. The primary advantages of LED-based luminaires include high energy conversion and optical efficiency, durability, lower operating costs, etc. The massive improvements in LED technologies have displayed efficient and robust full-spectrum lighting sources that achieve a variety of lighting effects in many applications. Some of the luminaires feature a plurality of lighting modules, including a plurality of LEDs, which are capable of generating different colors and color-changing lighting effects.
Today's digitally-based intelligent lighting control systems switch and dim luminaires, as they set up light scenes and manage them in space and time, thus allowing luminaires to be addressed individually and provide great flexibility. Their user-friendly features include easy programming and operations along with a simple installation process. Lighting control systems can be integrated as a subsystem into a building management scheme. A lighting control network consists of one or more lighting devices, e.g., electrical ballasts, LED devices, and dimmers. The dimmers must support specific interfaces to be able to receive control inputs and dim the lights appropriately. Different light devices may support different control interfaces.
LED-based luminaires do not usually fail abruptly like traditional light sources; instead, their light output slowly diminishes over time. Furthermore, LED light sources can have such long lives that life testing and acquiring real application data on long-term reliability becomes problematic—new versions of products are available before the current ones can be fully tested. To add to the challenge, LED light output and useful life are highly dependent on the electrical and thermal conditions that are determined by the luminaire and system design.
Luminaires embedded with LEDs are finding application in every shape and size in varied environments, such as homes, industrial factories, shopping malls, hospitals, office buildings, and so on. The primary reason for the immense popularity of this kind of luminaires is their operational longevity and their reduced power consumption. Lower power consumption helps people reduce their electric bills to a massive extent. Due to this, the technological advancement of these kind of luminaires has soared to new heights.
Smart luminaires embedded with LEDs also include a plurality of sensors, which may include daylight sensors, various kinds of field strength sensors used to sense electrical and magnetic fields, temperature sensors, motion sensors, light sensors, proximity sensors and so on. Smart lighting fixtures have been designed that additionally or alternatively implement intelligent lighting control systems in order to achieve energy savings. Each sensor has its own individual goals and responsibilities. To explain this with one example, some luminaires include daylight sensors and motion detectors. Each luminaire only illuminates when the ambient light level, as measured by the daylight sensor, is below a certain level, and this can be combined with a detected motion.
Existing technology discloses techniques to sense magnitudes of lumen depreciations in a number of ways. These systems sense a lumen depreciation of part of any lighting fixtures, but they also sense the relative light level external to the lighting fixtures. These systems are capable of not only deriving lumen depreciation levels of the luminaires but also the total lumen depreciation levels of the lighting fixtures. These systems typically are comprised of sensors positioned outside of the lighting fixtures, and comparators to determine measured actual lumen output signals from the sensors to pre-set references or threshold lumen output values. Error signals are generated by the comparators if it is disclosed that the actual lumen output has gone below the reference or threshold lumen output levels. In these systems, the sensor location relative to the luminaire is an important factor. In addition, the sensor calibration that is based on the specific luminaire and environment is critical to accurate measurement of lumen levels. It would instead be desirable to provide a sensor system that could be continuously operated even if the sensor is moved relative to the luminaire over the life of the luminaire. It would also be desirable to provide a sensor system that can be automatically recalibrated if the specific luminaire in use is replaced.
Another existing technology provides techniques to control individual LEDs in LED-based illumination devices so that a desired level of luminous flux and desired chromaticity of the illumination devices can be maintained over any fluctuations in drive currents and temperatures. The illumination devices include a plurality of emission LEDs, a storage medium, an LED driver, a receiver circuit, and a control circuit. The storage medium maintains a table of calibration values correlating forward voltage and drive currents to chromaticity and luminous flux at a variety of temperatures for each of the emission LEDs. The LED driver and receiver circuit provide respective drive currents to the emission LEDs to produce continuous illuminations, and periodically turn the emission LEDs off to calculate operating forward voltages that develop across each emission LED. The control circuit determines whether a target luminance setting or a target chromaticity setting for the illumination device has changed, and, if so, determines new respective drive currents needed to achieve the target luminance setting and the target chromaticity setting using the operating forward voltages measured across each emission LED, the table of calibration values, and one or more interpolation techniques.
Another existing technology provides techniques to monitor the health of LED-based lights. These techniques describe the received data regarding LED junction temperatures, ambient temperatures, and drive currents associated with the LEDs, receiving pre-existing LED performance data sets. They determined the end of life of the LEDs based on the junction temperatures of the LEDs, the ambient temperatures, the drive currents associated with the LEDs, and the pre-existing LED performance data sets.
However, the largest drawback associated with existing systems is that the positions of the sensors are fixed, i.e., their locations are not changeable. In all the above existing systems, the sensor must be pre-calibrated prior to use. Therefore, any change in the sensor location (relative to the luminaire position) or replacement of the luminaire type itself requires calibration information to be supplied (from the manufacturer) for the new system to be set up. Plainly, if the locations of the sensors are changed relative to the luminaires that they are sensing, then none of the above disclosed systems will be able to function in an appropriate manner. Rather, they would all need to be re-calibrated first, which can be extremely time consuming to do. What is needed is a system and method that frees an installer and/or maintenance crew from issues and activities associated with sensor installation and recalibration.
Due to the large variety of luminaries and the rapid introduction of new luminaire architecture and designs, there is a need for a system and a method that is capable of working with any type of luminaire while being able to control the luminaire with sensor readings even if the position of the sensor(s) is changed with respect to the luminaire, or if the luminaire itself has been changed.